Add Nix CI workflow, update docs and cargo hash

flake.nix

@@ -70,8 +70,6 @@
         echo "    nix run              - Run production version"
         echo "    nix build .#develop  - Build development version"
         echo "    nix run .#develop    - Run development version"
-        echo ""
-        cargo run --locked -- -h
       '';
     };
   };